1. Field of the Invention
This invention pertains to stents for use in intraluminal applications. More particularly, this invention pertains to a novel structure for such stents.
2. Description of the Prior Art
Stents are widely used for numerous applications where the stent is placed in the lumen of a patient and expanded. Such stents may be used in coronary or other vasculature, as well as other body lumens.
Commonly, stents are cylindrical members. The stents expand from reduced diameters to enlarged diameters. Frequently, such stents are placed on a balloon catheter with the stent in the reduced-diameter state. So placed, the stent is advanced on the catheter to a placement site. At the site, the balloon is inflated to expand the stent to the enlarged diameter. The balloon is deflated and removed, leaving the enlarged diameter stent in place. So used, such stents are used to expand occluded sites within a patient""s vasculature or other lumen.
Examples of prior art stents are numerous. For example, U.S. Pat. No. 5,449,373 to Pinchasik et al. teaches a stent with at least two rigid segments joined by a flexible connector. U.S. Pat. No. 5,695,516 to Fischell teaches a stent with a cell having a butterfly shape when the stent is in a reduced-diameter state. Upon expansion of the stent, the cell assumes a hexagonal shape.
In stent design, it is desirable for the stent to be flexible along its longitudinal axis to permit passage of the stent through arcuate segments of a patient""s vasculature or other body lumen. Preferably, the stent will have at most minimal longitudinal shrinkage when expanded and will resist compressive forces once expanded.
According to a preferred embodiment of the present invention, an intraluminal stent is disclosed. The stent comprises a reticulated tube having an un-deployed diameter and expandable to an enlarged diameter. The tube includes a structural beam extending between first and second ends. The structural beam changes from a first geometry to a second geometry when the tube changes from the un-deployed diameter to the enlarged diameter. The structural beam includes first and second longitudinal elements each extending at least partially between the first and second ends and with a spacing between the first and second elements. Each of said first and second elements changes from the first geometry to the second geometry when the tube changes from the un-deployed diameter to the enlarged diameter for the spacing to remain substantially unchanged as the tube changes from the un-deployed diameter to the enlarged diameter.
FIG. 1 is a perspective view of a first embodiment of a stent according to the present invention shown in a rest diameter state and showing a plurality of stent cells each having a major axis perpendicular to an axis of the stent;
FIG. 2 is a plan view of the stent of FIG. 1 as it would appear if it were longitudinally split and laid out flat;
FIG. 3 is the view of FIG. 2 following expansion of the stent to an enlarged diameter;
FIG. 4 is a view taken along line 4-4 in FIG. 2;
FIG. 5 is a view taken along line 5-5 in FIG. 2;
FIG. 6 is an enlarged view of a portion of FIG. 2 illustrating a cell structure with material of the stent surrounding adjacent cells shown in phantom lines;
FIG. 7 is the view of FIG. 2 showing an alternative embodiment of the present invention with a cell having five peaks per longitudinal segment;
FIG. 8 is the view of FIG. 2 showing an alternative embodiment of the present invention with a major axis of the cell being parallel to an axis of the stent;
FIG. 9 is the view of FIG. 5 following expansion of the stent to an enlarged diameter;
FIG. 10 is a plan view of a first prior art stent as it would appear if it were longitudinally split and laid out flat;
FIG. 11 is the view of FIG. 10 with the stent modified for support beams to include parallel, spaced elements in accordance with the present invention;
FIG. 12 is a plan view of a second prior art stent as it would appear if it were longitudinally split and laid out flat; and
FIG. 13 is the view of FIG. 12 with the stent modified for support beams to include parallel, spaced elements in accordance with the present invention.